Radiation detection devices



July 20, 1965 w. A. SHURCLIFF Re: 25,821

RADIATION DETECTION DEVICES Original Filed May 13, 1952 FIG. 3

2614*. 4 INVENTOR United States Patent 25,821. RABIATi-GN DETE CTIGNDEVHCES William A. Shureliif, {Iamhririgt}, Mass, assignor to PolaroidCorporation, Cambridge, Mass-x, a corporation of Delaware Original No.2,739,625, dated Jan. 10, 1956, Ser. No.

287,535, May 13, 1952. Application for reissue June 5,

1956, Ser. No. 589,361

7 Claims. (Cl. 25071) Matter enclosed in heavy brackets appears in theoriginal patent hut forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

This invention relates to detection and more particularly to devices,commonly known as dosimeters, for detecting and measuring penetrativeradiation of the kind emanating from radioactive or fissionablematerials.

An object of the present invention is to provide a dosimeter fordetecting and measuring penetrative radiation, said dosimeter beingprovided with a detecting element which, after having been subjected toa predetermined quantity of penetrative radiation, is adapted to emitfiuorescent light of an intensity functionally related to said quantitywhen excited by a predetermined quality and intensity of additionalradiation.

Other objects of the present invention are: to provide a dosimeter ofthe above type wherein the detecting clement is composed of silverphosphate glass; to provide, in combination with such a dosimeter,reading apparatus for exciting a detecting element of the aforementionedtype and for measuring the intensity of fluorescent light emanating froma face of said detecting element; to provide a dosimeter of the abovetype comprising a base mounting at detecting element, and means forpredeterminedly positioning said base with respect to said readingdevice; to provide a dosimeter of the above type having a base whichforms with a cooperating cover member a Weather-tight, lighttightcasing, the geometrical dimensions of which are of the same order ofmagnitude as are those of the detecting element; and to provide acompact dosimeter comprising a casing of the above type, the covermember of which may be opened and closed readily to permit repeatedreading of the detecting element.

Other objects of the invention will in part be obvious and will in partappear hereinatfer.

The invention accordingly comprises the product possessing the features,properties and the relation of components, and the apparatus possessingthe construction, combination of elements and arrangement of parts whichare exemplified in the following detailed disclosure, and the scope ofthe application of which will be indicated in the claim.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing wherein:

FIGURE 1 is a partially exaggerated, perspective view of a dosimeterembodying the present invention with the components thereof unassembled;

FIG. 2 is, a cross-sectional View of the dosimeter of FIG. 1 with thecomponents thereof assembled; and

FIG. 3 illustrates diagrammatically a reading device for measuring thequantity, in roentgens, of penetrative radiation to which the dosimeterof FIGS. 1 and 2 has been subjected.

A dosimeter embodying the invention herein disclosed includes atdetecting element which, after being Subjected to a quantity ofpenetrative radiation, has the property of emitting fluorescent light ofan intensity functionally related to said quantity when excited by apredetermined Re. 25,821 Reissued July 20, 1965 quality and intensity ofadditional radiation. One example of a material of which such adetecting element may be composed is sliver phosphate glass. Aftersilver phosphate glass has received a dose of gamma radiation, it hasthe property of emitting orange fluorescent light upon being excited bynear ultraviolet radiation. The intensity of this fluorescent light issubstantially proportional to the dose of gamma radiation. The dosimeteris so constructed that the detecting element is normally confined withina watertight casing formed by a base and a cover. When the cover isremoved two faces of the detecting element are exposed so that oneexposed face may be excited with ultraviolet radiation and the otherexposed face may emit fluorescent light, the intensity of which may bereadily measured.

Referring now to the drawings, wherein like numerals denote like parts,FlGS. 1 and 2 disclose a dosimeter embodying the present invention. As ameans for mounting and enclosing the components of the illustrateddosimeter, a casing 10 which includes a mounting means or base 12 and aclosure means or cover 14 is provided. Base 12 and cover 14 preferablyare composed of a material, such as an organic plastic, which does notappreciably attenuate radiation passing therethrough. Cover 14 isprovided with a suitable securing means 15 by virtue of which casing 10may be attached to the clothing of a wearer.

As shown, base 12 includes a head portion 16 and a peripherally threadedshank portion 18. Shank portion 18 is cut out to provide a space 2t)extending from its central section through a section of its periphery.Projccting from shank portion 18 into space 20 are a plurality of lugs22 which are adapted to predeterminedly orient a detecting elementwithin space 20.

Cover 14 is provided with an internally threaded opening 24! which isadapted to receive threaded shank portion 18. Base 12, when threadedinto cover 14, forms with cover 14 an easily opened and closed,lighttight, weathertight casing, the overall size of which may be of thesame order of magnitude as that of a detecting element positionedtherewilhin. A suitable gasket may be positioned between abutingportions of base 12 and cover 14.

in the illustrated embodiment, the detecting element comprises aphosphate glass parallelepiped 26 having a front face 28, a rear faceand four edge faces 32. Front and rear faces 28 and 30 may be polishedor, alternatively, may be rough ground to produce for example what isknown in the art as a 120 grit finish. Edge faces 32 may be polished or,alternatively, may be clean-cut by means of a conventional glass cutter.Element 26 is suitably secured within space 21 in such a manner thatfront face 28 and one edge face 32 are exposed. This construction andarrangement is such that if element 26 has received a dose of gammaradiation, when face 28 is illuminated with a predetermined intensity ofultraviolet radiation, fluorescent light predominantly in the orangerange of the spectrum, and of an intensity functionally related to thedose, emanates from exposed edge face 32.

An illustration of the composition by weight of a preferred detectingelement is as follows: approximately parts by weight of aluminumphosphate (Al(PO approximately 25 parts by weight of potassium phosphate(KPO approximately 25 parts by weight of barium phosphate (Ba(POapproximately 8 parts by weight of silver phosphate (Ag(PO preferably,the meta compound.

Excitation of element 26 with ultraviolet radiation produces withinelement 26 fluorescent light of a given intensity, part of whichemanates from exposed edge face 32. In the absence of preventativemeasures, such excitation further produces extraneous fluorescent lightin the immediate environment of element 26 which passes through element26 so as to cause the total intensity of fluorescent light emanatingfrom exposed edge face 32 to be greater than this given intensity. Inorder to prevent such extraneous radiation from passing through element26, all faces of element 26, excepting front face 28 and exposed edgeface 32, are provided with a black coating 34 which is adapted to absorbextraneous fluorescent light. Coating 34 further serves to eliminate anadditional source of error, namely, unpredictable reflection offluorescent light within element 26. By way of example, coating 34 maycomprise a black paint or enamel.

It has been found that the energy (measured in million-electron-volts),as Well as the dose or quantity of penetrative radiation, received bydetecting element 26 has an effect on the intensity of fluorescent lightemitted from exposed face 32. As a means for eliminating such energydependence," suitable radiation-attenuating shields may be providedthrough which penetrative radiation must pass in order to reach element26. It has been found, for example, that lead shields .ll6 mm. inthickness substantially eliminate energy dependence in the range of .05to 5.0 million-electron'volts. In the illustrated embodiment two leadshields of the aformentioncd type are secured to casing 10 adjaecnt ironand rear faces 28 and 30 of element 26. Thu base 12 is provided with ashield 36, square in shape, and sub stantially coextensive with face 30.Secured to cover 14 is shield 38 that is positioned parallel to andadjacent face 28 when base 12 and cover M are thlendcd together. Asshown, shield 33 is circular in shape and is sufficiently large to becoextensive with face 28 irrespective of the position which it assumeswhen base l2 and cover 14 are threaded together.

In accordance with the present invention there is provided a readingdevice for measuring the dose of penetrative radiation received by theabove-described dosimeter. A mounting means is provided forpredeterminedly orienting base 12 with respect to the remainder of thereading device. The mounting means. in the form shown, comprises amember 4 3 provided with a pair of pins 42 [one of which is shown indotted lines in FIG. 3), each of which is adapted to be inserted betweena pair of lugs 22 of shank portion 13. Member 40 is provided with anopening 44 which is aligned with face 28 of detecting element 26 whenpins 42 are properly inserted between the pairs of lugs 22 associatedtherewith.

A suitable source 46 of ultraviolet radiation is provided. In the formshown, viewing FIG. 3, source 46 is positioned below member 48 inalignment with opening 44 so as to be adapted to illuminate face 28 ofdetecting element 26. Since the intensity and character of fluorescentlight that emanates from edge face 32 is determined by the character ofradiation striking face 28, it is desirable to illuminate face 28 onlywith ultraviolet radiation of predetermined intensity and quality sothat fluorescent light emanating from edge face 32 will be preciselyrelated to the dose of radiation received by detecting element 26.Accordingly, there is positioned between source 46 and opening 44 asuitable filter 48 which absorbs all radiation except ultravioletradiation within a predetermined frequency range.

Forming part of a means for measuring the intensity of fluorescent lightemanating from edge face 32 is a photoelectric tube, designated hereinby 50. Fluorescent light emanating from exposed edge face 32 isreflected by a mirror 54 through a filter 56 toward the photoelectrictube. Mirror 54 is suitably curved to present a large solid angle sothat manufacturing to]- erances among the relative positions of themirror, the photoelectric tube and exposed face 32 do not appreciablyaffect the intensity of fluorescent light incident upon photoelectrictube Si Filter 56 is adapted to absorb all radiation passingtherethrough except orange light within a desired predeterminedfrequency range, which light bears a desired functional relationship tothe dose of gamma radiation received by detecting element 26.

in the illustrated embodiment, an alternating current power supply 53 isprovided to produce in source 46 pulsating ultraviolet radiation.Pulsating radiation from source 41) causes pulsating fluorescent lightto emanate from exposed e face 32 and to generate an alternati currentsi i .t the output of photoelectric tube 51!. nor evaluating thisalternating current signal, there is provided, as is illustrated at as,an amplifier for bringing the signal impressed thereon to a usefuldecibel a rectifier for converting the alternating current .tl to adirect current signal, and a microammeter fir providing a visualindicating of the intensity of the direct current signal. Themicroamrneter, if desired, may be calibrated in roentgens so as toindicate directly the of gamma radiation received by detecting cle-Photoclcctric tube 5% and amplifier, rectifier and micrcammcter 69, maybe energized by power supply in a conventional manner.

n operation, casing it) is assembled by threading i-t onto se 12 and isattached to the clothing by securin rucans l5, until it is desired nivcdby element 26. Cover 14 and base 32 mounted on member alt with betweenthe pairs of lugs 22 associated l low photoelectric tube 53 andamplifier, and micror'zmrneter 63 may be energized and cd by detectingelement 26 measured. 1 l sly to be understood that the principles hereindisclosed may be applied to dosimeters having detecting elementscomposed of materials other than hosphate glass.

Since certain changes may be made in the above product and apparatuswithout departing from the scope of the invention herein involved. it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustra tive and notin a limiting sense.

What is claimed is:

1. Detecting apparatus comprising a base, a cover capable of formingwith said base a casing, said base and said cover being composed of amaterial which is adapted to transmit penetrative radiation withoutappreciable attenuation, a phosphate glass detecting element mounted onsaid base, said element, after having received a dose of penetrativeradiation, being adapted to emit from one face thereof fluorescent lightof an intensity functionally related to said dose when excitingradiation of predetermined quality and intensity is incident uponanother face thereof, said other face being substantially at rightangles to said one face, and reading apparatus for measuring said dose,said reading apparatus comprising a mounting means, means forpredeterminedly orienting said base with respect to said mounting means,a source of ultraviolet radiation in alignment with said one face, aphotoelectric tube, a curved mirror positioned with respect to saidother face and said photoelectric tube so as to reflect fluorescentlight emanating from said other face toward said photoelectric tube andelectrical means for measuring the ignal produced by said photoelectrictube as a result of fluorescent light incident thereupon.

[2. A dosimeter comprising a base, a cover, said base having a headportion and a shank portion, the periphery of said shank portion beingexternally threaded, said shank portion being connected to said headportion at one of its ends and being free at the other of its ends, saidcover having an internally threaded opening therein, said shank portionhaving a cut-out space extending from its central section through asection of its peri hery and through its free end, and a phosphate glassdetecting ele ment secured in said cut-out space so that at least two ofto cv" its faces are exposed, said shank portion being threaded intosaid opening] [3. A dosimeter comprising a base and a cover, said basehaving a head and a peripherally threaded shank, one end of said shankbeing connected to said head and the other end of said shank being free,said shank having a cut-out space extending from its central sectionthrough a section of its periphery and through a section of its freeend, and a phosphate glass parallelepiped secured in Said cut-out spaceso that ultraviolet radiation may pass through said section of said freeend to one face of said parallelepiped and so that fluorescent light mayemanate from another face of said parallelepiped through said section ofsaid periphery, said cover having an internally threaded opening, saidshank being threaded into said opening in order to form with said covera Weather-tight casing for said parallelepiped] {[4, A dosimetercomprising a base, said base having a head portion and a shank portionhaving a threaded periphery, one end of said shank portion beingconnected to said head portion and the other end of said shank portionbeing free, said shank portion having a cut-out space extending from itscentral section through a section of said periphery and through asection of said other end, and a phosphate glass parallelepipeddetecting element mounted in said cut-out space, said element having oneface aligned with said section of said periphery and another facealigned with said section of said other end, said one face beingperpendicular to said other face, whereby ultraviolet radiation may passthrough said section of said other end and through said other face andso that fluorescent light emanating from said one face may pass throughsaid section of said periphery] 5. Apparatus for detecting and measuringgamma radiation, said apparatus comprising a dosimeter including a base,said base having a head portion and a shank portion, said shank portionbcing externally threaded, said shank portion being connected at one ofits ends to said head portion and being free at the other of its ends,said shank portion having a cut-out space extending from its centralsection through a section of its periphery and through its free end, anda phosphate glass detecting element mounted in said cut-out space withone face thereof exposed through said free end and another face thereof,at right angles to said first face, exposed through sail section of saidperiphery, said element, after having received a dose of penetrativeradiation, being adapted to emit from said other face fluorescent lightof an intensity functionally related to said dose when ultraviolet lightof predetermined intensity is incident upon said one fee said shankportion being adapted to be threaded into said opening, and readingapparatus for measuring said dose, said reading apparatus comprising amounting means, means for predeterminedly orienting said base with reseet to aid mounting means, a source of ultraviolet radiation forilluminating said one face, a photoelectric tube, a curved mirrorpositioned with respect to said other face and said photoelectric tubeso as to reflect fluorescent light emanating from said other face towardsaid photoelectric tube and electrical means for measuring the signalproduced by said photoelectric tube as a result of fiuorescent lightincident thereupon.

6. Detecting apparatus comprising a base, a cover capable of formingWith said base a casing, said base and said cover being composed of amaterial which. is adapted to transmit penetrative radiation Withoutappreciable attenuation, a detecting element mounted on said base, saidelement, after having received a dose of penetrative radiation, beingadapted to emit from one face thereof fluorescent light of an intensityfunctionally related to said dose when exciting radiation ofpredetermined quality and intensity is incident upon another facethereof, said other face being substantially at right angles to said oneface, and reading apparatus for measuring said dose, said readingapparatus comprising a mounting means, means for predetermincdlyorienting said base With respect to said mounting means, a source ofexciting radiation in alignment with said one face, a photoelectrictube, a mirror positioned with respect to said other face and saidphotoelectric tube so as to rcnect fluorescent light emanating from saidother face toward said photoelectric tube, and electrical means formeasuring the signal produced by said photoelectric tube as the resultof fluorescent light incident thereupon.

7. Detecting apparatus comprising a base, a cover c;- pable of formingwith said base a casing, said base and said cover being composed of amaterial which is adapted to transmit pcnetrative radiation withoutappreciable attenuation, a detecting element mounted on said base, saidelement, after having received :1 dose of penetrativc radiation, beingadapted to emit from one face thereof fluorescent light of an intensityfunctionally related to said dose when exciting radiation of preetermined quality and intensity is incident upon another face thereof,said other face being substantially at right angles to said one face,the remaining faces of said detecting element having a black coating,and reading apparatus for measuring said dose, said reading apparatuscomprising a mounting means, means for prcdetcrmincdly orienting saidbase with respect to said mounting means, a source of exciting radiationin alignment with said one face, a photoelectric tube, a curved mirrorpositioned with respect to said other face and said photoelectric tubeso as to reflect fluorescent light emanating from said face toward saidphotoelectric tube, and electrical means for measuriing the signalproduced by said photoelectric tube as a result of fluorescent lightincident thereupon.

[8. A dosimeter comprising a base, said base including a head portion ad a shank portion having a threaded periphery, one end of said shankportion being connected to said head portion and the other end of saidshank portion being free, said shank portion having a cut-out spaceextending from its central section through a section of said peripheryand through a section of said other end, and a parallelepiped detectingelement mounted in said cut-out space, said element having one face exposed at said section of said periphery and another face exposed at saidsection of said other end, said one face being perpendicular to saidother face whereby CR citing radiation may pass through said section ofsaid other end and said other face and whereby fluorescent lightenranating from said one face may pass through section of saidperiphery] E9. A dosimeter comprising a base, said base including a headportion and a shank porting having a threaded periphery, one end of saidshank portion being connected to said head portion and the other end ofsaid shank portion being free, said shank portion having a cut-out spaceextending from its central section through a section of said peripheryand through a section of said other end, and a paraiielpipcd detectingelement mounted in said cut-out space, said element having one faceexposed at said section of said periphery and another face exposed atsaid section of said other end, a black coating on the remaining facesof said clement, said one face being perpendicular to said other facewhereby exciting radiation may pass through said section of said otherend and through said other face and whereby fluorescent light emanatingfrom said one face may pass through said section of said periphery].

10. Apparatus for detecting and measuring gamma rudiation, saidapparatus comprising a dosimeter including a base, said base having ahead portion and a shank portion, said shank portion being externallythreaded, said shank portion being connected at one of its ends to saidhead portion and being free at the other of its ends, said shank portionhaving a cutout space extending from its central section through asection of its periphery and through its free end, and a detectingelement mounted in said cutout space With one face thereof exposed atsaid free end and another thereof, at right angles to said one face,exposed at said section of said periphery, said element, after havingreceived a dose of pcnetrative radiation, being adapted to emit, fromsaid other face, fluorescent light of an intensity functionally relatedto said close, when exciting radiation of predetermined intensity isincident upon said one face, said shank portion being adapted to bethreaded into said opening, and reading apparatus for measuring saiddose, said reading apparatus comprising a mounting means, means forpredeterminediy mounting said base on said mounting means, a source ofexciting radiation oriented toward said one face, a photoelectric tube,a mirror oriented between said other face and said photo: ectric tube soas to reflect fluorescent light emanating from said other face towardsaid photoelectric tube, and electrical means for measuring the signalproduced by said photoelectric tube as a result of fluorescent lightincident thereupon.

11. Apparatus for measuring gamma radiation, said apparatus comprising adosimeter including a base, said base having a head portion and a shankportion, said shank portion being externally threaded, said shankportion being connected at one of its ends to said head portion andbeing free at the other of. its ends, said shank portion having acut-out space extending from its central section througn a 'tion of itperiphery and ti rough its t re.) end, anel it Get. ing element mountedin said cutout space with one face thereof exposed at said free end andItttOll'tJ'l face thereof, .t right angles to said one face, expossd atsaid section of said periphery, the remaining faces of 'd element havinga black coating. said element, after having received a dose ofpcnetrative radiation, being adapte; to emit, from said other face,fluorescent light of an "ty functionally related to said dose, whenexciting radiation of predetermined intensity is incident upon said oneface, said shank portion being adapted to be thrc ed into said opening,and reading apparatus for measu: ng said dose, sa'd reading apparatuscomprising a mounting means, means for prcdeterminediy mounting saidbase on said mounting means, a source of exciting radiation orientedtoward said one face, a photoelectric tube. a curved mirror the axis ofwhich is oriented between said other ace and said photoelectric tube soas to reflect fluorescent light emanating from said other face towardsaid photoelectric tube, and electrical means for measuring the signalproduced by said photoelectric tube as a result of fluorescent lightincident thereupon.

12. Apparatus for detecting and measuring gamma radiation, saidapparatus comprising a dosimeter including a base, said base having ahead portion and a shank portion, said shank portion being externallythreaded, said shank portion being connected at one of its ends to saidhead portion and being free at the other of its ends, said shank portionhaving a cut-out space extending from its central section through asection of its periphery and through its free end, and a phosphateglass-detecting element mounted in said cutout space with one facethereof. exposed through said free end and another face thereof, atright angles to said one face, exposed at said section of saidperiphery, the remaining faces of said element having a black coating,said element, after having received a dose of penctrative radiation,being adapted to emit, from said other face, fluorescent light of anintensity functionally related to said dose, when ultraviolet light ofpredetermined intensity is incident upon said one face, said shankportion being adapted to be threaded into said opening, and readingapparatus for measuring said dose, said reading apparatus comprising amounting means, means for predeterminedly positioning said base on saidmounting means, a source of ultraviolet radiation oriented toward saidone face, a photoelectric tube, a curved mirror the axis of which isoriented between said other face and said photoelectric tube so as toreflect fluorescent light emanating from said other face toward saidphotoelectric tube, and electrical means for measuring the signalproduced by said photoelectric tube as a result of flaor scent lightincident thereupon.

References Cited by the Examiner The following references, cited by theExaminer, are of record in the patented file of this patent or theoriginal patent.

UNITED STATES PATENTS 1,576,535 3/26 Muir. 2,435,843 2/48 Rand.2,524,839 10/50 Schulman et al. 2,539,196 1/51 Marshall. 2,559,219 7/51Ludernan. 2,585,551 2/52 Hofstadtcr.

OTHER REFERENCES The Scintillation Counter, Coltman, Pro. of the I.R.E.,vol. 37, Jan.lunc 1949, pp. 671-682.

RALPH G. NILSON, Primary Examiner.

